Platform-canvas tightener.



No. 801,987. PATENTED 001. 17,1905. E. A. JOHNSTON.

PLATFORM CANVAS TIGHTENBR.

APPLICATION FILED MAR. 8. 1905.

NWN NWN WHQWYWWNW EDWARD A. JOHNSTON, OF STERLING, ILLINOIS.

PLATFORM-CANVAS TIGHTENER.

Specification of Letters Patent.

IPatented. Oct. 17, 1905.

Application filed March 8, 1905. Serial No 249,099.

To all whom it may concern:

Be itknown thatI, EDWARD A. JOHNSTON, a citizen of the United States,residing at Sterling,county ofWhiteside, Illinois,haveinvented certainnew and useful Improvements in Platform-Canvas Tighteners; and Idohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

The invention relates to tighteners for the canvas aprons that areemployed on the platforms of harvesting-machines. In this class ofdevices it is important that both edges of the canvas be held under thesame tension in order to prevent buckling of the same and so as to causeit to run evenly and straight instead of shirring off toward one end ofthe roller.

WVith these ends in view the invention consists in the particular meanshereinafter described and illustrated for causing the roller at theinner end of the platform to be held under a normal spring-pressuretending constantly to move it away from the roller at the outer end ofthe platform and arranged so as to bear with equal tension upon bothends of the movable roller so as to preserve its paralin slides e c,that move in ways provided for them on the inner sides of theplatform-boards a and b.

The platform-canvas is not illustrated; but it will be understood thatit runs over the rollers 0 and (Z, with its upper surface movingconstantly toward and over the inner roller and its front and rear edgessupported by the strips ff on the side boards a and b.

The roller-supporting slides e e are provided with transversely andinwardly extending projections g g] at the ends opposite therollerbearings, and levers it h are pivoted to the platform side boardsa and I) near the outer ends of the roller-slides so as to bear againstthese projections. By varying the length of the projections g g thedistances of the points of contact of the projections with the levers hh from the pivots of said levers may be changed, and thereby the extentof movement of the slides a e regulated. The levers h It are extendedinwardly toward each other and are connected at their inner ends by aslot-and-pin connection '6, so that any movement of one lever will causea movement of the other lever corresponding therewith in direction andextent. As'before stated, these levers bear against the projections g gof the roller-slides e c, and a spring 7', preferably a coiled spring,is pivotally connected at one end to one of the platform side boards,here shown as the rear side board a, and at its other end reacts againsta bracket 70, that is adjustabl y secured to one of the arms it andprojects outward laterally therefrom on the side toward the outer end ofthe platform, as shown in the drawing. The reaction of this springforces the levers h it toward the inner end of the platform and causesthem to bear with an elastic pressure on the projections of therollerslides, and the levers being of equal length and being connectedat their inner ends, as above described, tending to move the slidesinward with a uniform pressure.

When the platform-canvas is applied to the rollers, the levers h h arestraightened out into the position shown in dotted lines in the drawing.This permits the roller d to move slightly toward the fixed roller, andafter the ends of the canvas have been connected in the usual manner therelease of the levers 71v h by pushing on the roller-slides moves theinner roller d into the position shown in full lines and tightens thecanvas.

The ad just-ability of the bracket k provides for varying the tension ofthe spring 1', and the range of movement of the roller-slides may beregulated by making the projections g g of proper length.

Such being the construction of the tightener it will be noted that thesame amount of pressure and the same movement will be effected at eachend of the roller and that the parallelism of the movable. andstationary rollers will be preserved. It is also noticeable that theconstruction is simple, easily installed and adjusted, and efiicient inoperation.

Having thus described the invention, what I claim is- 1. Aplatform-canvas tightener, comprising, in combination with the platform,outer and inner rollers c, d, roller-slides e, 0 having projections g, gat their outer ends, and springpressed levers it, it, connected togetherat their inner ends and bearing on the projections of the roller-slides.

2. A platform-canvas tightener, comprising, in combination with thefront and rear side boards of the platform, outer and inner rollers 0,d, roller-slides e, e, in which the inner roller is mounted and havingprojections g, g at their outer ends, and levers h, it pivoted at theirouter ends to the side boards of the platform and bearing against saidprojections, said levers being connected together at their inner ends soas to move together equally and in the same direction.

3. A platform-canvas tightener, comprising, in combination with thefront and rear side boards .of a harvester-platform, outer and innerrollers 0. cl, roller-slides e, e in which the inner roller isjournaled, said slides having projections g, g at their outer ends,levers ii, h pivoted at their outer ends to the platform side boards andbearing against the projections of the roller-slides, said levers beingconnected at their inner ends by a pin-andslot connection d, and aspring pivoted to one of the side boards and bearing against a bracketprojecting from the outer side of one of the levers.

4:. A platform-canvas tightener, comprising outer and inner rollers, oneof said rollers being mounted in bearings adapted to slidelongitudinally relative to the canvas, springpressed levers connectedtogether at their inner ends and pivoted at their outer ends, each ofsaid levers engaging with one of said bearings between its pivot andinner end.

sliding bearings in which the inner roller ismounted and levers pivotedat their outer ends to said platform members and engaging with saidsliding bearings, said levers being connected together at their innerends so as to move together equally and in the same di rection, and aspring operative to move said levers in one direction.

7. In a platform-canvas tightener, the combination of front and rearplatform members, outer and inner rollers, sliding bearings in which theinner roller is mounted, and levers pivoted at their outer ends to saidplatform members and engaging with said sliding bearings, said leversbeing connected together at their inner ends so as to move togetherequally and in the same direction, and a spring operative between one ofsaid levers and one of said platform members to move said levers in onedirection.

In testimony whereof I afiix my signature in presence of two witnesses.

EDWARD A. JOHNSTON.

Witnesses:

FRED B. FRERIOHS, E. R. TnoMPsoN.

